Portion of a keyboard



FIG. 1 is a front perspective view of a keyboard showing my new design;

FIG. 2 is a top view thereof; and,

FIG. 3 is a rear view thereof.

The broken line showing of various regions in the Figures, the unshaded areas therein and the remainder of the keyboard is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a portion of a keyboard, as shown and described. 